In a medium-sized bowl, whisk together the egg yolk and Dijon mustard until well combined.
Slowly drizzle the vegetable oil into the bowl while continuously whisking. Keep whisking until the mixture starts to thicken and emulsify.
Once the mayonnaise begins to thicken, add the white vinegar or lemon juice and whisk until fully incorporated.
Season with salt to taste and continue whisking until the mayonnaise reaches your desired consistency.
Transfer the homemade mayonnaise to a clean jar or airtight container and refrigerate for at least 30 minutes before serving.
Enjoy your delicious, homemade mayonnaise on sandwiches, burgers, salads, or as a base for other flavorful sauces.
